Key difference: Risk is essentially the level of possibility that an action or activity will lead to lead to a loss or to an undesired outcome. The risk may even pay off and not lead to a loss, it may lead to a gain. Vulnerability, on the other hand, is a weakness that allows one to be exploited. It is a flaw that makes one susceptible to an attack, a loss or an undesired outcome.

Risk is essentially the level of possibility that an action or activity will lead to lead to a loss or to an undesired outcome. The risk may even pay off and not lead to a loss, it may lead to a gain.

Dictionary.com defines risk as:

• Exposure to the chance of injury or loss; a hazard or dangerous chance: It's not worth the risk.
• The hazard or chance of loss.
• The degree of probability of such loss.
• The amount that the insurance company may lose.
• A person or thing with reference to the hazard involved in insuring him, her, or it.
• The type of loss, as life, fire, marine disaster, or earthquake, against which an insurance policy is drawn.

There are many difference kinds of risk. Wikipedia lists six different ways that risk can be defined:

• A probability or threat of damage, injury, liability, loss, or any other negative occurrence that is caused by external or internal vulnerabilities, and that may be avoided through preemptive action.
• Finance: The probability that an actual return on an investment will be lower than the expected return.
• Food industry: The possibility that due to a certain hazard in food there will be an negative effect to a certain magnitude.
• Insurance: A situation where the probability of a variable (such as burning down of a building) is known but when a mode of occurrence or the actual value of the occurrence (whether the fire will occur at a particular property) is not.
• Securities trading: The probability of a loss or drop in value.
• Workplace: Product of the consequence and probability of a hazardous event or phenomenon.

Vulnerability, on the other hand, is a weakness that allows one to be exploited. It is a flaw that makes one susceptible to an attack, a loss or an undesired outcome.

Dictionary.com defines vulnerability as:

• Capable of or susceptible to being wounded or hurt, as by a weapon: a vulnerable part of the body.
• Open to moral attack, criticism, temptation, etc.: an argument vulnerable to refutation; He is vulnerable to bribery.
• (Of a place) Open to assault; difficult to defend: a vulnerable bridge.

Essentially, vulnerability increases the probability that a risk will lead to a loss or an undesired outcome. Vulnerability is the opening that might get exploited and bring about the loss. If the vulnerability is addressed and reduces, if not negated completely, it reduces the chance that a loss might occur and improves the probability of a risk paying off in a gain.

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